INTRODUCTION - Universiteit Twente · UNIVERSITY OF TWENTE. 19 GeoWebServices If webservices have...

UNIVERSITY OF TWENTE.

INTRODUCTION

Barend KöbbenITC–University of [email protected]

A SHORT INTRO TO THE WORLD-WIDE WEB

3©2012 – Dept. of Geo–Information ProcessingUNIVERSITY OF TWENTE.

HTTP communication

Client-server architecture

Browser

(Explorer, FireFox, Opera)

Webserver

(IIS, Apache, HTTPd)

Client Server

Can I have that file?

Here it is...


Request by URL

http://geoserver.itc.nl/roma02/index.html

Host & domain

Host & domain

PathPath

filefile

ProtocolProtocol

Uniform Resource Locator:


URL Protocol Prefxes

http: - Used to access HTML documents (web pages)

https: - http over a secured connection ftp: - Used to connect to an FTP site or

download a particular fle via FTP telnet: - Used to connect to a remote Internet

site using Telnet mailto: - Used to connect to an mail server

using SMTP etc…


a

abc

http:// www.itc.nl/file.html

The Simple Case

GET file.htmlSERVERSERVER CLIENTCLIENT

http://www.itc.nl/


a

abc

http:// www.itc.nl /file.html

file.html

The Simple Case

a

HTMLdocument<img src = “file.gif”> STATIC MAP

SERVERSERVER CLIENTCLIENT


a

abc

<img src = “file.gif”>

The Simple Case

GET file.gifSERVERSERVER CLIENTCLIENT


a

abc

http:// www.itc.nl /file.html

a

abc

The Simple Case

aa

abc

file.gif

file.gif

STATIC MAP



A Web Browser interprets an HTML document

Web pages are written in HTML: the Hypertext Markup Language

They may look different depending on hardware and browser


HTML = HyperText Markup Language

A brief history of HTML:

Originally developed by Tim Berners-Lee at CERN Popularized by the Mosaic browser developed at

NCSA (“oh please, no pictures...!”) Been extended in a number of ways.

Now in version HTML5 (not fnal)


HTML = HyperText Markup Language

HTML code = TEXT: the content, indepent of formatting +TAGS: two types of ‘commands’

formatting, eg:▶make text bold▶make text blue

(inter)activity, eg:▶<IMG src=“aFile.gif ”>show an image▶<A href=“aFile.html>link to a location</A>


HTML code

HelloWorld<HR>How areyou?<A HREF= ”otherfile.html”>Click here</a> to go.

Looks like:

Hello World How are you? Click here to go.


HTML5 Is the latest version of HTML (still under development) Is part of the “openWeb”: using only Open Standard

formats (e.g. making Flash unnecessary) Allows for MathML and SVG elements to be used inside

a document Combined with in-line JavaScript, it allows creation of

client-side web-applications

interoperability &

geowebservices

16 UNIVERSITY OF TWENTE.

Interoperability

Client

RequestRequest

Server

ResponseResponse

Software application



Software application Software

application


Server

Server



Server

To communicate between systems we need to standardise the messages between them


messagemessagemessagemessage

messagemessagemessagemessage


How to achieve interoperability?

make data seamlessly transferable & accessible Encode data in a standardized, platform & application

independent manner

access distributed functionality seamlessly Specify and set up an infrastructure of interoperable (software)

services, which encapsulate functionality and make it accessible via well specifed interfaces

XML

Web Services


Example

Currency converter with processable request and response: A fexible application using XML

many examples at http://www.webservicex.net/

<FromCurrency>USD</FromCurrency>

<ToCurrency >EUR</ToCurrency>

<double>0.92635</double>

RequestRequest

ResponseResponse


GeoGeoWebServices

If webservices have spatial functionality, for example if they use geographic data, can output maps or fnd routes, we call them geowebservices Google Maps, Bing maps, etc.: interfaces are publicly

available, but defned, developed and owned by commercial companies

Open Standard GeoWebServices: Open Web Services (OWS) of the Open Geospatial Consortium (OGC).


Plugins (client-side)

PDF-READER

a

abc

aa

abc

file.pdf

a

HTMLdocument<img src = “file.pdf”> interactive map

interactive map



SERVERSERVER

a

abc

10 March 2009

Client-side scripting (eg. JavaScript)

JavaScript interpreter

a

HTMLdocument

<script >



</script>

CLIENTCLIENT

22 UNIVERSITY OF TWENTE. a

HTMLin memory

server-plugin(Microsoft IIS

asp.dll)

Server-side scripting

(eg. Active Server Pages)

a

abc

database stuff

a

Database

a

HTMLdocument<img src = <%foundrec.image %> database stuff

<img src = map.gif> database stuff

SERVERSERVERCLIENTCLIENT


Query/Command by URL

Host & domain

Host & domain

PathPath

ApplicationApplication

ProtocolProtocol

http://localhost:8080/RIMapper/WMS?VERSION=1.1.1&SRS=4326

ParametersParameters


www.kartografie.nl/CGI?makemap

&title=“itc”

Server-side applications

(eg. CGI)

a

abc

itc

a

GIF file(virtual)

abc


a

Database

CGIAPPLI-

CATION

Open Geo Standards


Open STANDARDS created in an open, international, participatory process non-proprietary, that is, owned in common. free rights of distribution (no royalty or other fee) free, public, and open access to interface specifcations technology neutral

Open STANDARDS based software: employs Open Standard formats & interfaces can be proprietary, commercial or open source, free


Open Standard in Geo domainGeo domain

Open Geospatial Consortium (OGC) “our core mission is to deliver interface specifcationsc that are openly

available for global use”

Not-for-proft, international voluntary consensus standards organization industry, government, and university members Founded in 1994


OGC standardisation topics Topic 0 Overview Topic 1 Feature Geometry Topic 2 Spatial Reference Systems Topic 3 Locational Geometry Topic 4 Stored Functions and Interpolation Topic 5 The OpenGIS Feature type Topic 6 The Coverage Type Topic 7 Earth Imagery Topic 8 Relations Between Features Topic 9 Accuracy Topic 10 Feature collections Topic 11 Metadata Topic 12 OpenGIS Service Architecture Topic 13 Catalog services ...etcetera...


OGC Simple features geometry schema

UML representation of the Geometry schema

QuickTimeﾪ and a decompressor

are needed to see this picture.


Open Web Services & related EncodingsA set of Implementation Specifcations for

(vector) data encoding:Geographic Markup Language (GML)

Keyhole ML (KML)

Data Access:Web Feature Service (WFS)

Web Coverage Service (WCS)

Portrayal:Web Mapping Service (WMS)

Symbology Encoding / Styled Layer Descriptor (SE/SLD)

Processing:Web Processing Service (WPS)

Metadata:Catalog Service Web (CSW)


“Standardized interface for the creation of superimposed map-like views of geographic information”

WMS is actually the most mature and widest adopted OWS specifcation (numerous open source, as well as commercial solutions, e.g. WMS connector for ArcIMS)

Web Map Service (WMS)


WMS GetCapabilities

&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetCapabilities

<WMT_MS_Capabilities version="1.1.1">

<Service> ...service metadata (name, title, keywords, etc)…

</Service>

<Capability>

<GetMap>

<Format>image/gif</Format>

<Format>image/png</Format>

</GetMap>

<GetFeatureInfo>

<Format>text/plain</Format>

<Format>text/html</Format>

</GetFeatureInfo>

... other service parameters...

</Capability>

<Layer queryable="1" opaque="0" cascaded="0">

<Name>airports</Name>

<Title>airports</Title>

<SRS>EPSG:4326</SRS>

<BoundingBox SRS="EPSG:4326" minx="97.9" miny="6.5" maxx="104.8" maxy="19.9" /

</Layer>

...other layers...

</WFS_Capabilities>

<WMT_MS_Capabilities version="1.1.1">

<Service> ...service metadata (name, title, keywords, etc)…

</Service>

<Capability>

<GetMap>

<Format>image/gif</Format>

<Format>image/png</Format>

</GetMap>

<GetFeatureInfo>

<Format>text/plain</Format>

<Format>text/html</Format>

</GetFeatureInfo>

... other service parameters...

</Capability>

<Layer queryable="1" opaque="0" cascaded="0">

<Name>airports</Name>

<Title>airports</Title>

<SRS>EPSG:4326</SRS>

<BoundingBox SRS="EPSG:4326" minx="97.9" miny="6.5" maxx="104.8" maxy="19.9" /

</Layer>

...other layers...

</WFS_Capabilities>


WMS GetMap

&SERVICE=WMS

&VERSION=1.1.1

&REQUEST=GetMap

&LAYERS=forest,railroad,airports

&SRS=EPSG:4326

&BBOX=97.3,5.6,105.6,20.4

&WIDTH=400&HEIGHT=600

&FORMAT=image/png

Open SourceGeo Software


Open SOURCE software

Source code is freely accessible free for all to use, change and (re)distribute usually allowed to sell products that include source code

Development done in public: usually not by a company by a community: distributed, informal team of developers


Open source software (OSS) solutions

Advantages Low installation and maintenance

costs Independence of software vendors Large, open-minded and helpful user

community When documentation fails, code is

available for last resort Customisation: Can change

functionality to meet own’s needs

Disadvantages in some areas, proprietary solutions

(still) offer more functionality Documentation is often sparse Cannot force support Requires build-up of computer

literacy in own organisation: have to invest in people


Open source software STACK

(web)map-viewers, Graphic User Interfaces, desktop GIS, etcetera

thin clients thick clients

middleware: geo-webservicesdata-, map- and process services

Back-end: spatial databases

LIBRARIES: software components for :•data access•conversion•analysis•projection•graphics•etc...


The OSGEO stack in this course

PrototypeMozillaQt

GDAL/OGR

Proj4

Geotools/GEOS

Open Geo Data

40Barend Köbben (GIP)UNIVERSITY OF TWENTE.

OPEN DATA

Open Data is maybe more important than Open Source

without data, software means nothing most data is still

proprietary currently there is considerable movement to public access of geo-data

EU INSPIRE initiative OpenStreetMap Netherlands moves to OpenData:

data “basisregistraties” since 2012 opendataoverheid.nl PDOK demo gives an overview: http://nieuwsinkaart.nl/pdok/ Enschede “open data stad” (opendataenschede.nl)

Nov 23, 2014Nov 23, 2014Nov 23, 2014Nov 23, 2014 http://live.osgeo.orghttp://live.osgeo.orghttp://live.osgeo.orghttp://live.osgeo.org 41414141

OSGEO - Open Source Geospatial Foundation

– a not-for-profit organization

–mission to support and promote the collaborative development of open geospatial technologies and data.

– provides financial, organizational and legal support

– serves as an independent legal entity to which community members can contribute code, funding and other resources

– serves as an outreach and advocacy organization

– publishes the show-case OSGEO LiveDVD

http://live.osgeo.org/



Insert and Reboot




Thumb Drive & Virtual Machine




OSGeo-Live




Want to know more?

http://live.osgeo.org

OSGeo Foundationhttp://osgeo.org

Conferences:http://foss4g.org




http://osgeo.org/

http://foss4g.org/

46UNIVERSITY OF TWENTE.

INTRODUCTION TO THE WORKSHOP

we will employ the OSGeoLive system to: use a JS library (Leafet) to build a webpage that:

▶ shows a layer of Open Data (from OpenStreetMap) prepare a data layer (using QGIS) publish that data using OGC Open Standard WMS

(using GeoServer) use Leafet again to extend the webpage to:

▶ show the WMS layer and combine it with the OSM layer learn about and use Spatial Data Infrastructure technology

in geoportals

… and discuss the implications of this technology for your organisations

47UNIVERSITY OF TWENTE.

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INTRODUCTION - Universiteit Twente · UNIVERSITY OF TWENTE. 19 GeoWebServices If webservices have...

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